Analysis of temporal and attentional aspects of movement control.

The 5s performed a primary movement task and a two-choice reaction time (probe) task simultaneously. Both the number of possible actions, as conveyed by the signal, and precision of movement associated with the primary task were variables. The attention needed to perform the primary task was probed at one of several intervals following the primary task signal. Both the time and attention necessary to prepare a movement were related to the number of possible alternative actions associated with the primary task, but neither was related to the precision required to perform a movement. Conversely, the time and attention needed to complete a movement once it had begun was a function of movement precision, but not of the number of primary task signal alternatives.